You're right there's no way to unclick but you can script it.
It's a clunky workaround though, adding an event handler on the table row click event and storing the selectedRow in a temp variable. Compare the row click event with the last clicked one and if it's the same clear selection and if it's different set the variable.
Alternatively have a custom button on the table footer that's called "clear selection"
Example:
forum.json (387.7 KB)